Currently available methods of measurement of the dynamic characteristics of the lower esophageal sphincter (LES) are limited almost exclusively to the determination of lower esophageal sphincter maximum pressure (LESP) by an assortment of means. The LES has other characteristics which determine its competence besides pressure. These are LES length (SL) and LES radial asymmetry. Other factors which affect LES competence are the challenge pressures which it must withstand and its opening pressure (LESOP). Sphincter location may also play a role. The objective of this proposal in the determination of the relative contribution of each of these to LES resistance/competence (LESR/C) and the simultaneous development of a new method of esophageal motility testing, computerized axial manometry (CAM) of the LES which will simultaneously measure and correlate those determinants of LESR/C proven to be significant in its establishment. In order to carry out this investigation, a form of multivariate analysis will be used. In this presentation, LES competence will designate that property of the LES which absolutely prevents or stops gastroesophageal reflux. LES resistance will designate the actual resistance of the LES to backflow and is a measure of the degree of incompetenceof the LES. Absolute resistance to backflow equals competence.